In a large pot, bring salted water to a boil and add the diced red and white potatoes. Cook until tender, about 10-12 minutes.

Drain the potatoes and let them cool completely in a large bowl.

Once cooled, add the blueberries, cucumbers, and red onion to the bowl with the potatoes.

In a separate small bowl, whisk together the mayonnaise, apple cider vinegar, Dijon mustard, salt, and pepper.

Pour the dressing over the potato mixture and gently toss until everything is evenly coated.

Cover the salad and refrigerate for at least 30 minutes to allow the flavors to meld.

Before serving, garnish with fresh parsley and adjust seasoning if necessary.